The effects of feeding by the Russian wheat aphid (RWA). Dutraplu.s nom! ordvilko and the Bird cherry-oat aphid (BC A). Rhopaloppluan pad, L on he transport capacity of barley Holdeum vulgare L leaves were nvestigated and compated with a view to i-elan ng these effects to the isible symptoms shown by the respective infested plants RWA causes xtensive chlorosis and neciosis on an infested plant whereas I3CA auses no obseivable symptoms Our results using the xenobiotic. phloem obile Bum ophole. 5, 6 carboxyBurn escei n chacetate (5. 6-CFDA) evealed striking ch fletences in damage to the transpol t of ssimilates thiough the phloem by these two aphids The result clearly uggests that short-term feeding by RWA causes a reduction in tiansport f assimikites and a mole severe reduction oi pei haps even permanent essation of transport during long-term feed111,2. In contrast. feechntz y BCA does not lead to a !milked dect ease in transport do ring hort-term feeding period. howevei, a !eduction in the uanspoit was ecorded donne long-term feeding activities These iesults perhaps uggest that damage to ti ansport capacities of the barley leaves ppeals lobe partly responsible for the observed symptoms in WIA-infested plants and the lack of them during BCA in symptoms such as eduction ol cessation in transport of assionlates to growing tissues ay lead to such observable symptoms